Summary:
A solar wind stream hit Earth on Oct. 11th, sparking the strongest
geomagnetic storm of 2008. The brief but intense disturbance registered
7 on the 0-to-9 K-index scale of geomagnetic activity. See also
September 2008.

When magnetometer
needles began to swing at the Polar
Light Center in Lofoten, Norway, researcher Rob Stammes
knew something was up. "A geomagnetic storm was underway."
The storm began on Oct. 11th when a solar wind stream hit
Earth's magnetic field. Stammes' magnetometer recorded the
impact and subsequent reverberations, which lasted for hours.
In the chart
recording, red shows how the local magnetic field was
swinging back and forth while blue denotes electrical currents
surging through the ground in response. Outside, Northern
Lights were pulsating in sych with the chart recorder's
colored pens. "The ground current fluctuated with a
5-to-10 second period; the visible auroras were switching
on and off in the same way," he says. "It was
a really special sight."